In the treatment of fabrics in a tumble dryer it is known to add one or more conditioning agents together with the load to be dried. For instance, for imparting a softening benefit to fabrics it is known from CA 1,005,204 to co-mingle fabrics in a tumble dryer with a flexible substrate carrying a normally solid fabric conditioning agent. In co-mingling fabrics with impregnated substrates, however, there is a risk that the conditioner may not be evenly distributed. Furthermore, the co-mingling of the fabrics with impregnated substrates requires the separation of the substrate from the fabrics after the completion of the tumble dryer treatment. This separation is often time-consuming in that the substrates cannot readily be located.
Other disadvantages of such products include uneven product distribution following entanglement of the substrate with fabrics which can lead to greasy marks on fabrics (staining) and the tendency of such substrates to become positioned over the tumble dryer vent, thus giving virtually no benefit to the fabrics during a tumble drying cycle. Furthermore, these products are designed for single use only and therefore need to be replaced after every cycle. In addition, perfume delivery from the substrate onto fabrics is often poor resulting in consumers using additional substrates to deliver adequate perfume which is wasteful of resources.
For overcoming these problems it has been suggested, for instance in GB 2,066,309 and U.S. Pat. No. 3,634,947, to use conditioner dispensing articles, comprising means for attachment of the substrate to the tumble dryer wall. Other proposals, such as for instance disclosed in GB 1,399,728, involve the use of separate means for attaching the conditioning article to the tumble dryer wall.
EP-B-361593 concerns an alternative approach in which a fabric conditioning article comprises a combination of a substrate and a fabric conditioning composition, the substrate being a porous material with a specified void volume and cell count. The article of EP-B-361593 is designed to adhere to the tumble dryer wall.
U.S. Pat. No. 4,053,992 discloses a hemispherical device that fits onto the door of a tumble dryer and delivers fabric conditioner from sheets.
U.S. Pat. No. 5,787,606 discloses a dispenser on the door of a tumble dryer containing a roll of tumble dryer sheets.
WO-A-97/42290 discloses solid compositions that can be delivered by any convenient applicator fixed to the door or to the surface of the drum of the tumble dryer.
U.S. Pat. No. 5,040,311 discloses a device for use inside a tumble dryer for delivering a conventional aqueous fabric conditioners where the fabric conditioner migrates outwardly to the surface of the device to become engaged with clothes because of the heat and tumbling in the dryer. Staining from such liquid fabric conditioners that “wet” fabrics is mentioned.
U.S. Pat. No. 5,966,831 discloses a foam carrier for the inside of a tumble dryer impregnated with microencapsulated fluid where the microcapsules rupture because of mechanical and heat action.
U.S. Pat. No. 4,642,908 discloses a valve-containing device attached to the non-rotating head of a tumble dryer drum for delivering accurate and metered amounts of a fluid.
U.S. Pat. No. 4,014,105 discloses a device with multiple openings for the inside of a tumble dryer. Aqueous liquid conditioners are referred to, but the product is permanently in a liquid state and thus does not address the problem of leakage from the dispensing device during storage.
EP-A2-0539025 discloses fragrance microcapsules for fabric conditioning. The microcapsules are spray dried and incorporated into a tumble dryer article.
EP-A1-0459821 discloses a liquid fabric conditioning composition and an article for conditioning fabrics in an automatic laundry dryer. The liquid composition is not heat activated and the tumble dryer article does not container water.
U.S. Pat. No. 5,425,887 discloses a tumble dryer article comprising a fabric conditioning composition having little or substantially no free water.
In our co-pending applications, WO-A1-02/33160 and WO-A1-02/33161, there are disclosed articles suitable for treatment fabrics in a tumble dryer. The compositions of the present invention are particularly suitable for use with such devices.
In order to optimise the delivery of the active material onto fabrics during the drying cycle, it is desirable to provide a fabric treatment composition which, at a temperature below the heating cycle temperature of the tumble dryer, remains substantially within a dispensing article and is capable of undergoing a transition during the heating cycle of a tumble dryer such that it can be dispensed from the dispensing article
It is, therefore, desirable to provide a fabric treatment composition which is capable of undergoing such transitions without unacceptable instability. It is particularly desirable that the composition can undergo such a cycle repeatedly.
U.S. Pat. No. 4,014,432 relates to a product for fabrics treatment in tumble drying machines. Disclosure is made of conditioning agents which are normally solid at room temperature and soften sufficiently at the tumble dryer operating temperature to be exuded through perforations within the product. The conditioning agent is preferably a quaternary ammonium fabric softening agent in admixture with a nonionic surfactant. A very brief reference is made to aqueous solutions or dispersions and, in the examples, compositions comprising either a 1.8% aqueous solution of 3-alkoyloxy-2-hydroxypropyl trimethyl ammonium chloride or a 4.8% aqueous solution of lauryl dimethyl ammonio propane sulphonate are disclosed. There is no reference to the consumer perceivable problem of staining.
Effective delivery of a fabric treatment composition from a device such as described above requires the composition to be flowable at the delivery temperature (i.e. the heating temperature of the tumble dryer). The inventors have identified a problem with fabric treatment compositions which are suitable to be delivered onto fabrics in a liquid state in that they can leave stain marks on the treated fabric.
Fabric staining is referred to in U.S. Pat. No. 5,066,413, U.S. Pat. No. 4,049,858, WO-A-97/42290 and U.S. Pat. No. 4,149,977. However, this is in relation to tumble dryer sheet conditioning compositions only.
The problem of staining is particularly associated with distributing a substantially liquid product during the heating cycle of a domestic tumble dryer. For this reason, liquid fabric treatment compositions are usually delivered in a washing machine rinse cycle and not in a tumble dryer heating cycle.
Without wishing to be bound by theory, the applicants believe that the visibility of such stains originates from the reduction in the reflection of light from the surface of the stained fabric compared to the reflection from adjacent unstained part of the fabric. More particularly, the visibility of the stain is due to the difference in the refractive index of the fibre of the fabric and that of the composition delivered.
It is also believed that the level of staining is affected by whether the delivered composition fills the spaces between fibres or spreads on the fibres themselves. The stain becomes more visible if the air between the fibres is replaced with the composition since this reduces the difference in refractive index between the fibre and the surrounding fabric giving rise to more transmitted light and less reflection.
The visibility of a stain is also believed to be affected by the thickness and evenness of spreading of the composition onto fabrics. Thin, even spreading of the composition is most desirable and thus viscosity and surface tension characteristics of the fabric treatment composition which improve thin, even spreading are particularly desirable.
Nevertheless, a composition which is delivered as a liquid onto fabrics is desirable since it is believed that a liquid will be dispensed and distributed evenly during delivery.
Accordingly, it is desirable to provide a heat activated fabric treatment composition which can be delivered as a liquid during the heating cycle of a tumble dryer from a dispensing device and which addresses the problem of staining.
Furthermore, it is desirable to provide a heat activated fabric treatment composition which delivers anti-static benefits. Additionally, it is desirable to provide good perfume longevity and/or perfume substantivity to fabrics treated using the compositions of the invention.
It is further desirable to provide a heat activated fabric treatment composition which can be stored in a dispensing device and which can undergo repeated cycles from a more viscous storage state to a less viscous dispensable state such that during the heating cycle of the tumble dryer at least part of the composition is delivered to fabrics.